1. Field of the Invention
The present invention relates to an electric apparatus using a rechargeable battery, and more particularly, to a system and method for automatically indicating that a battery should be replaced in an electric apparatus having a power adaptor.
2. Description of the Related Art
Batteries are used in most electric devices, such as portable computer, wireless phone, audio and video equipment, etc. Typically, battery monitoring apparatus and method have been widely used for detecting the voltage or the capacity of the battery and notifying an user the detected voltage or capacity of the battery. In order to provide an user with exact information about the state of the battery, the battery monitoring apparatus and method have used a controller to detect the voltage and the capacity of the battery. The controller of the battery monitoring apparatus, however, need more complicated structures to calculate the voltage and the capacity of the battery while user can not be informed of the exact information about the battery. I have found that with conventional battery monitoring apparatus and method, the structure becomes more complicated, and that it is impossible to correct or otherwise improve the conventional apparatus and method in order to get a more perfect apparatus and method for detecting and indicating that the battery should be replaced or the battery should be abandoned.
In an effort of detecting voltages of the battery and notifying an user when the battery was discharged or should be recharged, various types of controller connected to the battery have been used in electrical machine for detecting voltages of the battery. For example, U.S. Pat. No. 5,047,961 for an Automatic Battery Monitoring System issued to Simonson discloses an instrument monitoring of emergency stand-by batteries during operation of the batteries. The instrument records the conditions of the batteries as well as alerts the operators when the discharge operation. U.S. Pat. No. 5,196,779 for a Battery Maintenance System issued to Alexandres et al. discloses a battery maintenance system for charging, analyzing, discharging and conditioning of a battery. The system displays voltage and capacity to determine whether or not the battery has enough capacity to power equipment for an optimal time period. U.S. Pat. No. 5,321,627 for a Battery Monitor And Method For Providing Operating Parameters issued to Reher discloses a battery monitor monitoring the operating parameters of a battery, for example, the absolute state of charge, the relative state of charge, and the capacity of the battery. U.S. Pat. No. 5,459,671 for a Programmable Battery Controller issued to Duley discloses a controller controlling and motoring charge level, temperature, discharge and recharge of a rechargeable battery. U.S. Pat. No. 5,569,550 for a Battery Pack Having Under Voltage And Over-Voltage Protection issued to Garret et al. discloses a battery system for disconnecting a battery before overcharge condition occurs. I have noticed that the embodiments described by these references do not indicate that the battery should be replaced or abandoned because these references provides only the states of charge, discharge, or recharge in the battery.
Since the above battery monitoring apparatus and methods of detecting the voltages of the battery are insufficient to represent the state of the battery, the alternative methods have been used in the electrical machine for calculating an amount of electric capacity of the battery. In general, a battery initially provides a maximum amount of the electrical capacity which is determined by properties of the battery. The electrical capacity of a battery is indicated by ampere-hour and watt-hour. The ampere-hour is determined by multiplying electric current output from the battery by a period of time for which the battery can be used. The watt-hour is determined by multiplying electric power output from the battery by a period of time for which the battery can be used at the output electric current. Since watt is determined by multiplication of electric current by voltage, the ampere-hour and watt-hour can be converted from one to the other. Since one of either ampere-hour or watt-hour of a battery is measured in an electric apparatus, the other can be obtained. The amount of the electrical capacity can be a standard for determining how long a battery can be used in an electric apparatus.
The electrical capacity varies according to the numbers of time and environment of use. Generally, when about 5% of the total electrical capacity in a battery is left, an electric apparatus hardly works which is referred to as a "low battery" state. Then, the electric apparatus can be used again by replacing it with another battery or recharging the battery if it is rechargeable. Here, the criterion of the low battery state can be determined according to the type of electric apparatus and rechargeable battery for use. In an electric apparatus requiring high degree of precision such as a portable computer, the criterion of a low battery state is very strict, while the criterion of a low battery state is not strict for an electric apparatus which is not demanding a high degree of precision such as a portable illuminator.
Particularly, when a rechargeable battery is discharged and recharged repeatedly, the electrical capacity of the recharged battery becomes lower than the initial electrical capacity of the new battery. A rechargeable battery installed in an electric apparatus generally repeats the discharge and the recharge when in use and then the amount of the electrical capacity of the battery becomes low. Thus, the repeated recharge of the battery shortens the life of the battery. Assuming that the amount of electrical capacity of a rechargeable battery when it is manufactured is 100, it is generally regarded as an appropriate time to replace the battery when the amount of electrical capacity of the rechargeable battery is 50 or less with respect to the initial amount of the initially completely recharged electrical capacity. When it is the most appropriate to replace or abandon the battery depends on the remaining amount of the electrical capacity of the battery or the type of the electric apparatus or battery.
However, it is not easy for user to know when to replace or recharge the battery during using the battery. The user usually anticipates the proper time by experience or should always carry extra batteries for unexpected situations. Since the case of batteries for notebook computers which are relatively large, heavy, and expensive, it is inconvenient to carry extra batteries. Moreover, a DC/DC power board including a power supplying unit and a recharging unit in a rechargeable electric apparatus only supports a function for recharging a built-in rechargeable battery when the external electric power is applied to the rechargeable electric apparatus. Accordingly, when the rechargeable electric apparatus is used at a place where there is no supply of the electric power, the power adapter cannot be used for recharging the battery. A nearly discharged battery causes lots of inconvenience. Furthermore, even if the power adapter is be used, it is inconvenient since a user cannot predict when to replace the battery.
For the purpose of calculating the state of capacity and the life time of the battery and informing an user of when the battery should be recharged, various types of complicated microcontroller and peripheral equipment are used. For example, U.S. Pat. No. 5,278,487 for a Battery Conditioning System Having Communication With Battery Parameter Memory Means In Conjunction with Battery Conditioning issued to Koenck discloses a battery monitor system monitoring battery operation and calculating and displaying battery capacity. U.S. Pat. No. 5,565,759 for a Smart Battery Providing Battery Life And Recharge time Prediction issued to Dunstan discloses a smart battery predicting the remaining life and recharge time of the battery based on battery-specific characteristics. I have found that these embodiments need the more complicated process and apparatus in order to calculate the state of the battery and do not provide an indication that the battery should be replaced or abandoned.